1. Field of the Invention
The present invention relates to a dielectric member, a piezoelectric (electrostriction) member, and a producing method therefor, and more particularly to a dielectric member and a piezoelectric member applicable to a capacitor, a sensor, a transducer, an actuator and the like. It is particularly suitable for a ferroelectric memory which is recently attracting particular attention, a MEMS device or an ink jet head. Also the piezoelectric member is applicable, in addition to an ink jet head, to a memory head, an optical shutter and a speaker.
2. Description of Related Background Art
A dielectric material of a high specific dielectric constant is required for capacitors, while a thin layer formation of a ceramic material such as BaTiO3 is progressing for obtaining compact capacitors. However a material such as BaTiO3 or Pb(Zr,Ti)O3 has a specific dielectric constant of about 1,500 at maximum in a ceramic material, and a thin layer formation may provide electronic devices of unsatisfactory characteristics due to an imperfect sintering or an interfacial structural defect.
There is recently investigated also an application of an (111) oriented PZT layer with a stable residual polarization to a memory. An example of preparing a (111) layer is described for example in Japanese Patent Application Laid-open No. 2003-179278. In this method, a (111)-oriented YSZ layer is formed as a buffer layer on a Si substrate, and SrRuO3 (SRO) (111) is formed utilizing a lattice thereof, thereby obtaining a PZT(111) layer. This method is however associated with drawbacks that a formation of a buffer layer is required, that a stress control is required because a stress in the buffer layer influences the performance of the produced device, and that a layer of a tensile stress formed by such stress control is unable to stably grow the crystallinity of the SRO(111) layer thereon. Also such process, relying on an epitaxial growth, is poor in reproducibility. For avoiding these drawbacks, there is desired a monoaxially oriented layer of a uniform orientation, for which reproducible characteristics can be expected.
In the field of a piezoelectric member, owing to the recently expanding investigations for MEMS and piezoelectric applications, there is desired a piezoelectric element with satisfactory characteristics in a thin layer. The piezoelectric element is an element showing an extension/contraction when an electric field is applied between electrodes sandwiching a piezoelectric member, and is applicable to a motor, an ultrasonic motor, an actuator and the like.
A material utilized in these fields is a PZT material discovered about 50 years ago. A PZT material has a sintering temperature of 1100° C. or higher, and a material development is investigated for example by a sol-gel method, a sputtering method, an MBE method, a PLD method, a CVD method or the like for obtaining a thin layer device. However, a thin layer structure is associated with a drawback of easily causing a physical destruction in the layer or at the layer interface.
Therefore, it is being tried to obtain a layer of a large piezoelectric constant or a satisfactory voltage resistance. An example of utilizing a (001) oriented layer formed by sputtering in an ink jet head is described in Japanese Patent Application Laid-open No. H8-116103. In this method, an oriented electrode is provided on a substrate to control a crystalline structure of the piezoelectric layer. In this method, through a (001) oriented Pt electrode can be formed with a satisfactory crystallinity on a single crystal MgO substrate, there are involved drawbacks that the single crystal MgO substrate is expensive and is limited in the substrate size.